Link Pay (Mobile App or Browser Redirect)

// Backend: Create Link Pay order
app.post('/api/checkout/link-pay', async (req, res) => {
  const { orderId } = req.body;
  const order = await getOrder(orderId);

  const response = await rebellAPI.linkPayCreate({
    productCode: process.env.REBELL_PRODUCT_CODE,
    paymentRequestId: `checkout-${order.id}-${Date.now()}`,
    paymentAmount: {
      currency: 'EUR',
      value: order.totalCents
    },
    order: {
      orderDescription: order.description,
      merchant: {
        store: {
          externalStoreId: process.env.STORE_ID
        }
      }
    },
    settlementStrategy: {
      settlementCurrency: 'EUR'
    }
  });

  // Store payment reference
  await updateOrder(order.id, {
    paymentId: response.paymentId,
    paymentRequestId: `checkout-${order.id}-${Date.now()}`,
    status: 'pending_payment'
  });

  res.json({
    redirectUrl: response.redirectUrl,
    appLinks: response.appLinks,
    paymentId: response.paymentId
  });
});

// Frontend: Handle redirect
async function initiatePayment(orderId) {
  const response = await fetch('/api/checkout/link-pay', {
    method: 'POST',
    body: JSON.stringify({ orderId })
  }).then(r => r.json());

  // Detect platform and redirect
  const isMobile = /iPhone|iPad|Android/i.test(navigator.userAgent);
  const isIOS = /iPhone|iPad/i.test(navigator.userAgent);

  if (isMobile) {
    const url = isIOS
      ? response.appLinks.ios.shortUrl
      : response.appLinks.android.shortUrl;
    window.location.href = url;
  } else {
    // Show QR code for desktop users
    showQRCode(response.appLinks.android.shortUrl);
  }

  // Start polling for status
  pollPaymentStatus(orderId);
}

// Frontend: Poll for payment completion
async function pollPaymentStatus(orderId) {
  const maxAttempts = 60; // 5 minutes with 5-second intervals
  let attempts = 0;

  while (attempts < maxAttempts) {
    await new Promise(resolve => setTimeout(resolve, 5000));

    const order = await fetch(`/api/orders/${orderId}`).then(r => r.json());

    if (order.status === 'paid') {
      showSuccess('Payment completed!');
      return;
    } else if (order.status === 'failed') {
      showError('Payment failed. Please try again.');
      return;
    }

    attempts++;
  }
}

// Webhook handler
app.post('/webhooks/rebell', async (req, res) => {
  // Verify signature
  if (!verifySignature(req)) {
    return res.status(401).send('Invalid signature');
  }

  const { paymentRequestId, result } = req.body;

  if (result.resultStatus === 'S') {
    await updateOrderByPaymentRequestId(paymentRequestId, { status: 'paid' });
    await fulfillOrder(paymentRequestId);
  } else {
    await updateOrderByPaymentRequestId(paymentRequestId, { status: 'failed' });
  }

  res.status(200).send('OK');
});